The death toll in a massive suicide blast in Pakistan's north-west reached 35, officials said today, as the country prepared for the widower of the former prime minister, Benazir Bhutto, to take over as president.

The attack yesterday demonstrated the severe militant threat facing the Muslim nation and president-elect Asif Ali Zardari, who overwhelmingly won MPs' votes the same day as the blast and was expected to be sworn in by Tuesday.

Zardari has vowed to be tough on militancy, a stance that plays well in Washington which has pushed Pakistan to clamp down on extremist havens along its borders.

Zardari has a fine line to walk. Coming down too hard on insurgent activity risks inflaming Pakistani public opinion and even a tribal uprising. But he also faces pressure from opponents to reduce the powers of the presidency, which he and his party have vowed to do.

Ahsan Iqbal, a spokesman for the chief opposition party, told Dawn News Television that Zardari's election was simply a stop along the way to restoring full democracy in Pakistan, and that the transition required giving up some of the president's powers.

The president has the power to dissolve parliament and appoint army chiefs, and chairs the joint civilian-military committee that controls Pakistan's nuclear weapons.

"Parliament is sovereign," Zardari told a group of well-wishers on Saturday. "This president shall be subservient to the parliament."

Dozens were wounded in Saturday's attack, in which an explosives-packed pick-up truck blew up at a police checkpoint on the outskirts of Peshawar in the north-west. Police said a huge amount of explosives was used in the blast, signalling that the attacker might have been aiming for a more important target.

Television footage showed a blast crater 3 feet (1 metre) deep, destroyed vehicles and pieces of debris scattered across a large area. Some buildings in a nearby market collapsed, leading civilians to dig frantically with their hands to find survivors.

A teacher and school guard were among the five dead newly recovered from the rubble, police official Rashid Khan said.

The Election Commission said today that Zardari's win had been certified. His aides said he could be sworn in within a couple of days.

Newspaper editorials marking Zardari's ascent noted that a recent US-led ground assault in a tribal region along the Afghan border signalled American impatience with Pakistan's progress in battling insurgents.

Far from being confident, however, the opinion pieces warned that Zardari is yet unproven and still tainted by a history of corruption allegations.

"What Mr Zardari needs to do is to dispel the impression that he is a political wheeler-dealer who is adept at making back-room deals but unable to rise to the requirements of statesmanship," said an editorial in Dawn, a leading English-language newspaper.